The present invention relates to a storage battery comprising a plurality of cells enclosed within a housing, each cell containing electrolyte and plates coated with positive or negative active mass and separated by separator plates, and the requisite electrical connectors interconnecting the plates and/or cells.
Conventional storage batteries made from lead are in general composed of plates enclosed within a cell and immersed in electrolyte. In the cell there is a conducting part conveying the current, a plate frame produced from lead or lead alloy, and active mass which, in general, is pasted in the plate frames. The sides of the plate frames are provided with lugs by which they are soldered to leaden current rails, which in turn are soldered to one another through partitions of the cells.
When discharging the storage battery at high currents, the resistance of the plate frames limits the operation of the storage battery in that the active mass only in the vicinity of the plate lugs is efficiently used. For assuring an adequate the current flow, large quantities of lead have to be placed in the plate frames, which increases the weight of the storage battery. In addition, storage battery housings are used in conventional storage batteries in which the partitions between the cells are used. Not many conductors can be transmitted through the partitions to conduct current from one cell to another. A deep storage battery housing with these partitions is in itself an expensive plastic part which is difficult to produce.
Also, there are storage battery designs which deviate from the conventional one, such that part of the electrodes have been constructed to be bipolar. The positive and negative active masses of the adjacent cells are pasted on the same plate frame, which at the center point has been engaged to a plastic frame in conjunction with injection molding. The plastic frames have been soldered to one another with ultrasonic waves so that the partitions of the cells and, at the same time, the entire storage battery become well sealed. An advantage of this storage battery its small internal resistance and uniform use of active material, which is a consequence of the contact from one cell to another, the contact being distributed uniformly in the area of the entire partition of the cell. One drawback is that a very great number of joints must be made by soldering, which increases the production costs of the storage battery.
Known in the art are also the so-called recombination storage batteries (see e.g. EP 01 07 976) in which the plates containing the positive and negative mass of the adjacent cells have been connected with bridging pieces. The bridging pieces may, in fact, be composed of projections connecting plate parts belonging to adjacent cells. In this storage battery, between the plate stacks constituting the adjacent cells there are no sealed partitions but merely an air gap. The structure is workable only in the instance in which the electrolyte has been absorbed into the separator plates and active masses. A drawback is, for instance, that leakage current flows on the surface of the conductors along the electrolyte diaphragm, the disadvantage becoming greater, the broader the connecting pieces between the plates. Also, the flow distribution is partly uneven because all of the current that flows must pass through the above-noted projections.